One of the lead coffins, with gold-painted mitre, found in the vault beneath St Mary-at-Lambeth.
Photograph: Craig Dick

The remains of five archbishops of Canterbury have been found beneath a medieval church next to the current archbishop’s official London residence, it has been revealed, much to the delight of Christians celebrating Easter.

The discovery at the deconsecrated church of St Mary-at-Lambeth was made during the refurbishment of Lambeth Palace’s Garden Museum last year, and has been kept secret for months while work was finished.

The redevelopment team, led by site managers Karl Patten and Craig Dick of building contractors Rooff, accidentally came across the dark entrance to the tomb when they began stripping back the flagstones from the church.

After uncovering a set of stairs under a slab, they fashioned a long torch out of a mobile phone attached to a stick and were able to have the first glimpse of what lay beneath: a hidden crypt that contained 30 lead coffins.

Patten told the BBC: “We discovered numerous coffins – and one of them had a gold crown on top of it.” Archbishops were often buried with gold-painted mitres – ceremonial headpieces – placed on their coffins.

While the identity of some of the remains are a mystery, three of the coffins have nameplates. These belong to Richard Bancroft (the archbishop from 1604 to 1610, who chaired the committee that wrote the King James Bible), John Moore (archbishop from 1783-1805) and his wife, Catherine Moore.

Frederick Cornwallis (in office 1768-1783), Matthew Hutton (1757-1758) and Thomas Tenison (1695-1715) have also been identified as being laid to rest at the church, alongside John Bettesworth, the dean of the arches (an ecclesiastical judge) between 1710 and 1751.

Visitors to the Garden Museum will be able to view the undisturbed coffins through a glass floor-panel. Photograph: Garden Museum

Considering Lambeth Palace has been the residence of the archbishop of Canterbury, the Church of England’s most senior cleric, for nearly 800 years, it is little surprise the remains date back as far as the 17th century.

Burials were known to have taken place in the churchyard, but it had been assumed that the vaults under the church had since been filled with earth.

So far the coffins have been left undisturbed, though the builders have installed a glass panel in the floor above them so visitors can peer into the crypt.

The Garden Museum, which has been closed for its £7.5m redevelopment since 2015, will reopen on 22 May.